Duration impulse receiver



May Z7, 1947. o. T. FRANCIS 2,421,022

DURATION IMPULSE RECEIVER Filed Jan. 4. 1945 2 Sheets-Sheet l May 27, 1947 o. T. FRANCIS 2,421,022

DURATION MPUEsE RECEIVER Filed Jan. 4, 1945 2 Sheets--Sheei' 2 [iimhhhlmw Y SMM Patented May 27, 1942 UNITED STATES PATENT loi=1=lcE DURATION IMPULSE RECEIVER Oliver T. Francis. Benville, Minn.

Application January 4, 1945, Serial No. 571,315

17 Claims. (Cl. 177-353) a cyclic pattern and repeated several times to perform one function at the receiving station. Such systems use slow release, or slow pick up mechanical relays or Ya combination of both as the decoding means. In view of the mechanical inertia involved in mechanical relays high speed transmission has been impossible with such systems. Furthermore the mechanical relays are subject to deleterious eiects such as those resulting from change in temperature, wear, etc.. and therefore can never be made` very accurate. It is one of the objects of this invention to prolvide a system whereby the operations performed by the slow pick up mechanical relays may be performed entirely by vacuum tube relays, thereby getting away from such undesirable features.

Another object is to provide a signalling receiver for a signal pattern comprising two impulses of different durations separated by a spacing, a iirst reactance device inwhich the energy is changed at a predetermined rate for the vduration of said impulses. a second reactance device in which the energy is changed for the duration of the spacing and means for recording said energy changes as an indication of the signal received.

Another object is to provide a receiver having a plurality of condensers, vacuum tubes for charging said condensers, means for discharging a rst of said condensers at a predetermined rate from the beginning of the first oi said impulses to the end of the last impulse, and discharging a second of said condensers from the end of said first impulse to the end of said second impulse, and discharging a third of said condensers from the beginning of the last impulse to its end. and

means for indicating the charges remaining on said condensers at the end oi said impulses.

Another object is to provide a novel means of rendering a receiving unit operable only at the end of the signal.

Another object is to provide a system of cross connections between signal responsive vacuum tubes whereby the maximum number of electroresponsive devices may be selectively operated by the minimum number of tubes.

These and other objects will become apparent from the claims, description and gures, wherein:

Fig. 1 shows a transmitter for producing a signal pattern of desired durations and spacings.

Fig. 2 shows a receiver for decoding said signals, and,

Fig. 3 shows several signals which may be transmitted.

Referring to Fig. l, I have shown a means for producing time displaced impulses of variable duration and spacing, comprising a means for producing a source of voltage varying in magnitude, and a plurality of vacuum tubes each of said tubes being conductive between dierent magnitudes of said voltage, for producing the patterns of signal voltages such as shown in Fig. 3.

The source of variable voltage consists of a neon tube oscillator comprising the series connection of a B" battery i, a gas discharge device 3, and the parallel connection of condenser t and resistance 5. The grid of vacuum tube t is connected to the positive4 terminal of resistance 5. The output circuit of tube can be traced from the positive terminal of battery i, primary oi' transformer l, plate impedance of tube t, to the ground 2 terminal of battery i. The grid of vacuum tube t ,is connected through resistance 2t, and secondary of transformer l to the negative terminal of battery i. The output circuit of tube t can be traced from the positive terminal of battary I, through plate impedance of tube 8, potentiometer l0, the plate impedance of vacuum tube il to the negative terminal of battery l. Vacuum tube il is a screen grid tube and has a high A. C. plate impedance. It is shown as a pentigrid converter tube having its rst, second, and fourth grids connected to its cathode and its third and fth grids connected together internally and to battery i at a more positive point than its cathode. Condenser 9 is connected between the cathode of tube il and the negative terminal of battery l.

Vacuum tubes l2 and i3 are conductive to plate current at diierent magnitudes of`volta`ge across condenser 9. Various types of vacuum tube circuits conductive to input voltages between predetermined magnitudes are known. I prefer to use the pentigrid converter type as described in my above application Ser. No. 499.757. The iirst grid ot-tube i3 is connected through resistance 20 to a point on potentiometer it. Its anode grid is B connected to the positive terminal o! battery I. through resistance 2|. and to the negative .terminal of battery I throughvoltage divider Il. Its cathode ls connected to ground 2. Its screen grid is connected to a terminal of battery I more positive than ground. Its fourth grid is connected to an intermediate point on divider Il. l

Similarly vacuum tube I2 has its ilrst grid connected through resistance I3,- to potentiometer I near the cathode of tube 3. Its cathode is connected to ground 2. Its anode grid is c onnected through resistance 2l to the positive terminal of battery I, and through voltage divider I5 to the negative terminal of battery I.

on voltage divider I5.

Since tubes I2 and |3 both have high A. C. plate impedances it is essential to emciency that the load in their output circuits be of high A. C. impedance also. This load consists if a vacuum tube I6 which may be oi the pentigrid converter type. Its cathode is connected to the negative terminal of battery I1. Its ilrst grid is connected through resistances 21 and 22 to the positive terminal of battery I1. Its anode grid may be left disconnected. Its third and fth grids are connected together internally and to the positive terminal of battery I1. Its fourth grid is connected through resistances 23 and 23 to the positive terminal oi battery I1.

The output circuit of tube I2 can be traced from the positive terminal of battery plate impedance of tube I6, battery I'I, resistance 22, plate impedance of tube I2 to the ground terminal of battery I.

The output circuit of tube I3 can be traced from the positive terminal of battery I. through the plate impedance of tube I6. battery I1, resistance 23, plate impedance of tube I3, to the ground terminal of battery I. Resistance 2l is Its fourth grid is connected to an intermediate pointf connected between outgoing line I3 and ground 2.

The operation of Fig. 1 in producing signal patterns such as shown in Fig. 3 is as follows. Gas discharge device 3 breaks down at a frequency depending on the constants of the neon oscillator circuit charging condenser 4 and impressing a positive potential on the grid of tube E causing a surge of current through the primary of transformer 1 and a positive potential of brief duration to be impressed on the grid of tube 8 through resistance 25. Condenser 0 is charged through the plate impedance of tube 8.

When condenser 9 is fully chargedv a positive potential is impressed on the first grids of tubes I2 and I3, .rendering them non-conductive to plate current. 'Ihe reason that tube I3 is nonconductive to plate current when a positive potential is impressed on its tlrstgrid through resistance 20 is that a large current flows from the positive terminal of battery I through resistance 2|, to its anode grid and cathode, producing a large voltage drop across resistance 2|. a portion of which voltage drop is applied to its fourth grid by voltage divider I4.

As condenser 9 discharges through potentiometer I0 and the plate impedance of tube Il the i-lrst grid of tube I3 assumes a slightly negative potential with respect to its cathode. 'Ihe voltage drop across resistance 2| is` decreased, and the fourth grid of tube 3 assumes a positive potential. The fourth grid of tube I3 being positive and its first grid slightly negative a current passes from the positive terminal of battery I, through the plate impedance of tube I0, battery I1.' resistance 23. the plate impedance oi' -tube I3. to the groundfterminal of battery I until its nrst grid is sumciently n egative to block current. The voltage drop across resistance becomes more than the voltage oi' battery I1. The fourth grid of tube Il becomes negative. and its plate impedance very high. The cathode oi' tube I3 becomes negative and a negative impulse is impressed on line I3. Ihe duration of this negative impulse depends on where the fourth grid` oi tube I3 is connected to voltage divider Il. If it is connected to the lower portion ol' voltage divider Il the rst grid of tube 1|3 must be turther negative to block current producing a voltage drop across resistance 2| and tube I3 is conductive to plate current for a shorter period such as shown in pattern |23 of Fig. 3 between TI and T2. It on the other hand the fourthgrid of tube I3 is connected to the upper portion oi voltage divider Il, tube I3 is conductive to plate current over a greater magnitude of voltage variation of its ilrst grid, producing a negative impulse such as shown ir. pattern |21 of Fig. 3 between T9 and T6. It is apparent that desired patterns such as shown in Fig. 3 can be produced across line I0 and ground by keying the points where the fourth grids'of tubes I2 and I3 connect to their respective voltage dividers I5 `and I4, and the point where the first grid of tube I2 connects to potentiometer I0.

Fig. 2 shows a means for receiving the variable spaced variable duration impulses shown in Fig. 3, and decoding them to operate any one of a plurality of electro-responsive devices 83-9l. Line I8 is connected through resistance 3| to the grid of vacuum tube 32, and through condenser 80, and resistance 8l to the grid of vacuum tube H0. The grid of vacuum tube IIO is also connected to its cathode through resistance 81. `The plate of tube |I0 is connected through resistance 98 to the positive terminal of battery 30, and through condenser 99 and resistance |00 to the grid of vacuum tube |0|. The output circuit of tube |0| can be traced from the positive terminal of battery 30, the plate impedance of tube |0I, condenser |02, to the negative terminal of battery 30. The grid of tube I 0| is connected to the negative oi' battery 3 0 through the plate impedance of vacuum tube III, in parallel with high resistance Ill. The grid of tube ||l is connected tothe negative terminal of battery II2. The positive terminal of that battery is connected through resi/stance ||3 to the anode of vacuum tube 8|. Potentiometer |03 in series with the plate impedance of high A. C. impedance screen grid tube |03 is connected across condenser I02. Vacuum tube |04 is here shown as of the pentigrid converter type. Its first, second and fourth grids are connected to its cathode. Its third and fifth grids are connected together internally and to a terminal of battery 30 more positive than its cathode. Vacuum tube 53 may be of the pentigrid converter type. Its ilrst grid is connected through resistance 60 to a point on potentiometer |03 near the cathode of tube IM.

Its anode grid is connected to the positive ter-v vacuum tube 81. Resistance 61 isin the common input output circuit of tube 81. y 4

Vacuum tube |06 may also be of the pentigrid converter type. Its first grid is connected through resistance |08 to a point on potentiometer |03. Its anode grid is connected through resistance |01 to the cathode of tube 48, and to the negative terminal of battery 30 through voltage divider |09. Its third and fth grids are connected to a positive terminal of battery 30. Its output circuit includes the positive terminal of battery 30, primary of transformer |05, plate impedance of tube |06 and ground terminal of battery 30. The secondary of transformer is connected between ground and the grid of vacuum tube 66. The plate of tube 66 is connected to the positive terminal ofbattery 30. Resistance 65 is connected in its common input output circuit.

The output circuit of tube 32 can be traced from the positive terminal of battery 30, through the primary of transformer 33, the plate impedance of tube 32, condenser 34 to the negative terminal of battery 30. In parallel with condenser 34 is potentiometer 35 and the high A. C.

plate impedance of vacuum tube 38, which latter tube may be of the pentigrid converter type. The irst, second, and fourth grids of tube 38 are connected to its cathode. Its screen grid is connected to battery 30 at a point more positive than its cathode.

Vacuum tubes 54 and 55 may be of the pentigrid converter type. Their rst grids are con: nected to potentiometer 35 so that their plate impedances will be conductive to space current` for different magnitudes of voltage across condenser 34. One=terminal of the secondary of transformer 33 is connected to the negative terminal of battery 30. The other terminal is connected through resistance 40 to the grid of vacuum tube 39. The output circuit of vacuum tube 39 may be traced from the positive terminal of battery 30, through the plate impedance of tube 39, and condenser 4| to the negative terminal of battery 30. Potentiometer 42 and the high A. C. plate impedance of vacuum tube 8| is connected in parallel with condenser 4|. Vacuum tube 8| may be of the pentigrid converter type. Its rst, second, and fourth grids are connected to its cathode. Its third and fth grids are' connected together internally and to a terminal of battery 30 more positive than its cathode. Vacuum tubes 82 and 83 may be of the pentigrid converter type. Their first grids are connected to potentiometer 42 to render these tubes conductive to plate current at different predetermined magnitudes of voltage across condenser 4|.

The upper terminal of transformer 33 is also connected through condenser 46 in parallel with resistance 41 to the grid of vacuum tube 48. The output circuit of vacuum tube 48 may be traced from the positive terminal of battery 30, plate to cathode of tube 48 and through seven separate paths back to battery 30. A rst of these paths comprises resistancel 53 to ground terminal of battery 30. A second path comprises resistance 49, the anode grid, the cathode of tube 54 and ground 2. The third path comprises resistance 50, the anode grid, the cathode of tube 55 and ground 2. The fourth -path comprises resistance 5|, the anode grid, the cathode of tube 82 and ground. The fifth path comprises resistance 52, the anode grid, the cathode of tube 83 and ground. The sixth path includes resistance 5B, the anode 6 grid, the cathode of tube 59 and ground. 'Ihe seventh path includes resistance |01, the anode grid, the cathode of tube |06 and ground.

Potentiometers 63, 96, 12, 10 connect the respective anode grids of tubes 55, 54, 82, 83 to the negative terminal ofbattery 30.

The output circuit of tube 55 can be traced from the positive terminal of battery 30 through primary of transformer 56, the plate impedance of tube 55 to the ground terminal of battery 30. The output circuit of tube 54 can be traced from the positive terminal of battery 30, through -primary of transformer 51, plate impedance of tube 54 to the ground terminal of battery 30. The output circuit of tube 82 can be traced from the positive terminal of battery 30, through the primary of transformer 14, the plate impedance ofv tube 82 to the ground terminal of,battery 30'. The output circuit of tube 83 can be traced from the positive terminal of battery 30 through pri- Vacuum tubes 69, 1|, 13, 15 are of the Plural grid type and are here shown as pentigrid converters. Their cathodes are all connected to ground 2. Their third and fifth grids are connected to a terminal of battery 38 more positive than ground. Their anode grids are all left 'disconnected. One terminal of the secondary of transformer 56 is connected to the fourth grids of tubes 69, 13 through respective resistances 6|, 68. One terminal of the secondary of transformer 51 is connected to the fourth grids of tubes 1|, 15 through respective resistances 62, 85. One terminal of transformer 14 is connected to the first grids of tubes 69, 1| through respective resistances 11, 16. One terminal of the secondary of transformer 64 is connected to the rst grids of tubes 13, 15 through respective resistances 19, 18. The plates of vacuum tubes 69, 1|, 13, 15 connect through respective electro-responsive devices 95, 93, 90, 88 to the cathode of tube 66. The plates of tubes 69, 1|, 13, 15 also connect through respective electro-responsive devices 94, 92, 9|, 89

,pattern |25 of Fig. 3 is impresed on line |8, the

grid of vacuum tube ||0 receives a negative impulse at the beginning of the first impulse, that is at time TI. The plate of tube ||0 goes -positive and impresses a positive pulse on the grid of tube |0| through condenser 99 and resistance |00. At this instant the resistance of the path between the grid of tube |0| and negative of battery 30 is very high, since resistance ||4 is a very high resistance and the grid of tube is biased past its current cut off by battery ||2 connected to the plate of tube 8|. Condenser |02 charges through the plate impedance` of tube |0|. The grid of tube 32 is negative during the entire duration of the first impulse of pattern |25, and appreciablecurrent has leaked from condenser 34. At Ithe end of the rst impulse the grid of tube 32 goes positive and a current passes through the .primary of transformer 33 and its plate impedance to recharge condenser 34. The secondary of transformer 33 impresses a positive potential on the grid of tube 39 through resistance 40, charging condenser 4|. The secondary of transformer 33 also impresses a positive pulse on the grid of tube 48 through condenser 46 in parallel with resistance 41, producing a voltage drop across resistance 53, but the plate impedance of tubes 55, 54, 82, 83, |06, 59 are not effected thereby since their first grids are either too positive or too negative at that instant. I'he RC time element of resistance 41, condenser 46 is such as to render this surge voltage across resistance 53 very brief.

At the beginning-of the second impulse of pattern |25, that is at time T3, a negative pulse is again impressed on the grid of tube H0, a positive pulse is pamed through resistance and the plate impedance of tube to the negative of battery 30. 'I'his latter impedance is very low due to the fact that .condenser 4| is now charged and the plate of tube 8| highly positive,

At the end of the second impulse that is at T4, considerable current has leaked ofi' of condensers 34, 4|, and |02. Condenser |02 has been discharged from TI to T4 and the voltage impressed on the first grid of tube 58 renders it conductive to plate current when the cathode of tube 48 goes positive. The secondary of transformer 80 impresses a positive 'voltage on thel` Condenser 4| has discharged grid of tube 81. 4 from T2 to T4. Tube 83- is rendered conductive and a positive potential is impressed on the first grids of tubes 13 and 15. Condenser 34 has discharged from T3 to T4. Tube 54 is rendered conductive to plate current and a positive pulse is impressed on the fourth grids of tubes 1|, 15. Since all grids of tube 15 are positive current passes from the `positive terminal of battery 30 through the plate impedance of tube 81, electroresponsive device 89, the plate impedance of tube 15, to ground terminal of battery Y If a signal of a different pattern is received such as |26 of Fig. 3, condenser |02 discharges from Tl to T4,` rendering tubes 59 and 81 conductive. Condenser 4| discharges from T2 to T4 rendering tube 83 conductive and impressing a positive potential on the first grids of tubes 13, 15. Condenser 34 discharges from 'I5`to T4, rendering tube 5-5 conductive and impressing a positive potential on the fourth grids of tubes 69, 13. A current then passes from the positive terminal of battery 30 through the plate impedance of tube 81, electro-responsive device 9| of the plate impedance of tube 13 to ground.

If a pattern such as |21 of Fig. 3 is received condenser |02 discharges from T9 to T8, rendering tubes |06, 66 conductive, condenser 4| discharges from T6 to T8 rendering tube 82 conductive, impressing a positive potential on the irst grids of tubes 69, 1|. Condenser 34 discharges from T1 to T8 rendering tube 55 conductive and impressing a positive potential on the fourth grids of tubes .69, 13.v A current then passes from the positive terminal of battery 30, through the plate impedance of tube 86, electroresponsive device 95, the plate impedance of tube 69 to the ground terminal of battery 30.

Tubes 66, 81, 69, 1|13, 15 are of the high vacuum type. their use being preferred where practicable. Where, however, the electro-responsive devices require considerable power, the

trigger effect of grid controlled gas discharge devices makes possible control of large power by positive pulses of brief duration.

I have illustrated a system where only two magnitude discriminating tubes are supplied with input voltage by each of condensers 34, 4|, and |02, thereby making possible the operation of any one of eight electro-responsive devices 88-95'. The number of electro-responsive devices varies as the third power of the number of these tubes. That is with four voltage magnitude tubes connected across condensers 34, 4|, and |02 the number of electro-responsive devices would-be 64. It

would be a two impulse system using impulses and spacings of four different durations.

While av suflicient number of electro-responsive devices for most uses can be operated by two im- 5 pulse cyclically repeated patterns, where operation of a larger number of electro-responsive devices is necessary three and four impulse patterns may be used by rendering tubes 39, 48 inoperative by voltages existing across one or more of condensers at the end of the second and the beginning ofthe third impulse, as I have illustrated for tube |0| of Fig. 2.

It is obvious that my invention may take Widely diiferent vforms from those illustrated without 15 departing from its spirit, and it is to be limited in scope only as dened in the following claims.

What I claim is:

1. In a circuit for receiving time displaced impulses of different duration, as an indication oi' received intelligence, a plurality of condensers, means for varying the charge at a predetermined rate on a rst of said condensers from the beginning of a first of said impulses to the end of la last of said impulses, means for varying the charge at a predetermined rate on a second of said condensers from the end cf said first impulse to the end of said last impulse, means for varying the charge at a predetermined rate on a third of said condensers for the duration of said last impulse, and means for indicating the charge remaining on each of vsaid condensers at the end of said last impulse. as an indication of said intelligence.

2. In a circuit for receiving a signal pattern having impulse of different duration, a plurality of condensers, means-for charging said condensers, means for discharging a first of said condensers at a predetermined rate between the expiration of a rst of said impulses and the expiration of the last of said impulses, means for discharging a second of said condensers at a predetermined rate for the duration of said last im- L pulse, a plurality of electrorespon'sive devices,

and.means for operating one of said devices, de-

pending on the various charges remaining on said condensers.

3. In a circuit for receiving a plurality of impulses, a plurality of condensers, means for charging said condensers, means for discharging said condensers at predetermined rates as follows: a rst of said condensers from the beginning of a first of said impulses to the end of said last impulse, a second of said condensers from the end of said ilrst impulse tothe end of said last im- Pulse, a third of said condensers during said last impulse, a plurality of electroresponsive devices and means for operation of each of said devices by a different combination of remaining charges on said condensers.

80 4. In a circuit for receiving a signal pattern having a plurality of impulses, a plurality of vacuum tubes having input and output circuits, a plurality of condensers each connected in the input and output circuit of a separate one of said tubes, an impedance connected in parallel with each of said condensers, means for producing a positive pulse at the beginning of a rst of said impulses, means for applying said pulse to the input circuit of a rst of said tubes to charge a o first of said condensers, means for producing a second positive pulse at the expiration of said first impulse, means for applying said second pulse to the input circuit of a second of said tubes to charge a second of said condensers, a plurality of electroresponsive devices and means for operating anyone of said devicesdepending' on the combination of charges remaining on said condensers at the end of said impulses.

5. In a circuit for receiving a cyclic pattern of i impulses of different durations, a plurality of condensers, meansfor varying the charge on said condensers at predetermined rates as follows: a first of said condensers from the end of the iirst of said impulses to the end of the last of said impulses, a second of said condensers for the duration of said last impulse, means for indicating the charge remaining on said condensers at the end of said last impulse, said last means comprising a plurality of vacuum tubes, each of said tubes being conductive to plate current at a different magnitude of voltage across said condensers, means for rendering said tubes operative only at the end of said last impulse, a plurality of valves, each having a plurality of grids and an output circuit, a separate electroresponsive device connected in the output circuit of each of said valves, and means for selectively controlling said grids with said plate current of said tubes.

6. In a circuit for receiving a cyclic pattern of impulses and spacings of diierent durations, a plurality of vacuum tubes having input and output circuits, a source of current connected in the common output circuitl of each of said tubes, a separate condenser in parallel with a resistance connected in the common input output circuit of each of said tubes, means for producing pulses at the beginning and end of said impulses, means for applying said pulses to selected ones of said input circuits to charge a different one of said condensers with each of said pulses, means for preventing said pulses from beingxapplied to in put circuits other than said selected ones, said last means comprising a vacuum tube having a plate, filament, and grid, a second resistance, said second resistance, said plate and said lilament being connected in series across said means for producing said pulses, means for connecting said plate and filament in said input circuit, and means for controlling the potential of saidl grid by the voltage across one of said condensers in the input and output circuit of a dierent one` of said tubes. y

7. In a circuit for receiving a signal having a pattern of a plurality of impulses, means for producing a first series of pulses, one at the beginning of each of said impulses, means for producing a second series of pulses, one at the end of each of said impulses, Aa plurality of condensers, means for charging a first of said condensers by a first pulse of said first series, said last means comprising a vacuum tube having a control. electrode, an input and an output circuit, a resistance in parallel with said iirst condenser connected in said input and said output circuit, means for applying said iirst series of pulses to said input circuit through a second resistance, a second vacuum tube having a plate, filament and grid, said plate being connected to said control electrode, said filament being connected to the negative terminal of said first condenser, means for controlling the potential of said grid by voltage variations across a second of said condensers to short circuit a second pulse of said first series, means for charging a second of said condensers with a rst impulse of said second series, a plurality of electroresponsive devices and means for operating one of said devices depending on the charge remaining on said condensers at the end of said pattern.

8. A circuit for indicating the duration of an 10 impulse comprising: a vacuum tube having an input and an output circuit, a source of current and the primary of a transformer connected in said outputcircuit, acondenser connected in said input and said output circuit, a, potentiometer in series with the plate impedance 'of 'a screen grid tube connected across said condenser, a plurality of pentigrid converter tubes, means for connectlng the rst grid of each of said tubesto a different point on said potentiometer, a separate plate load connected in the plate circuit of each 4of said pentigrid tubes, a separate anode grid load connected in the circuit of the anode grid of each of said pentigrid tubes, means for applying a portion of the voltage variations across said anode grid load to the fourth grid of each of said pentigrid tubes, a thermionic valve having an anode, a cathode and a grid, means for connecting` said source of current inthe circuit of said anode of said valve, means for connecting said anode grid loads of each of said pentigrid tubes in parallel in the common anode grid circuit of said valve, means for applying a positive pulse from the secondary of said transformer to said grid to said valve at the end of said impulse to render one of said pentigrid tubes conductive to plate current depending on the charge remaining on said condenser at the end of said impulse, and means for indicating voltage variations across said plate load.

9. A circuit for indicating the duration of an impulse, comprising: a vacuum tube having an input and an output circuit, a source of current and the primary of a transformer connected in said output circuit, a condenser in parallel vwith a resistance connected in said input and said output circuit, a plurality of plural grid vacuum that said impulse produces a voltage drop of very brief duration across said second resistance, means for applying voltage variations across said second resistance to one -grid of each of said plural grid tubes to render one of said last tubes conductive to plate current during said brief duration, and means for indicating said plate current.

l0. Ina circuit for receiving a signal pattern having a plurality of impulses of different durations, a plurality of condensers, means for discharging said condensers at predetermined rates during the following periods: a first of said condensers from the beginning of the first of said impulses to the end of the last of said impulses, a second of said condensers during said last impulse, a plurality of cathode follower vacuum tubes having a cathode, an input and an output circuit, means for applying a positive pulse to the input circuit of one of said tubes depending on the charge remaining on said first condenser at the end of said last impulse, a plurality of valves each having a plate, filament, and grid, a separate load connected between the cathode of Ieach of said follower tubes andthe plate of each of said valves, and means for impressing a positive pulse on the grid of one of said valves maining on said second condenser at the end of said second impulse.

11. In a'circuitv for receiving a signal pattern oia plurality of impulses, a plurality of condensers, means for varying the charge on said condensers at a predetermined rate from dierent points in said pattern to the end oi said pattern,

a plurality oi cathode follower vacuum tubes each` having an anode, a cathode anda control electrode, means for applying a positive pulse to the control electrode oi one of said tubes depending on the charge remaining on a ilrst of said condensers at the end oi said pattern, aplurality of vacuum tubes each having a plate, filament and grid, a separate load connecting themathode of each of said follower tubes to the plate oi each oi said vacuum tubes, and means for applying a rpositive pulse to theV grid of one of said vacuum tubes depending on the voltage of the charge remaining on a second of said condensers at the end of said pattern.

12. In a circuit for receiving a signal pattern of impulses and spacings, a receiver for said pattern, comprising: a plurality of sources of voltages variable at predetermined rates, means for actuating each of said sources at a different point in said pattern, a separate vacuum tube magnitude selective device, connected across each oi said sources, each device having a plurality of tubes each conductive to a diiIerent magnitude ci input voltage, a plurality of electro-responsive devices, and'means for operating one oi' said devices depending on the combination oi'y said tubes conductive at the end of said pattern.

18. In an electric circuit, means for initiating a plurality oi' varying voltages at time displaced intervals, a plurality of electroresponsive devices, and means for operating any one of said devices depending on the combination oi the instantaneous values of said voltages at a predetermined time subsequent to the initiation oi one of said variable voltages.

14. In an electric circuit, means for operating one of a plurality of electroresponaive devices depending on the combination of instantaneous values oi' a plurality of different voltages comprising: a plurality oi groups of vacuum tubes each of said tubes having an input and an output circuit, means for applying each of said voltages to said input circuit of diierent groups of said tubes, each oi' said tubes being conductive to space current for one value oi input voltage only, and means for operating any one oi said devices depending o n the combination of said tubes rendered conductive.

15. In a selective circuit, a plurality of vacuum tubes, a separate space charge control means in each oi said tubes for controlling space current in each oigsaid tubes, a plurality oi thermionic valves, each having an anode, a cathode-and a control electrode, a plurality o! vacuum tubes each having a plate, filament and grid. a separate electroresponsive device connecting each oi said cathodes to each o! said plates, means for controiling the potential of said control electrodes and said 'grids with said space current owing in dinerent ones oi said ilrst tubes to selectively operate said electroresponsive devices by said space current of said diiierent ones of said first tubes.

16. In a circuit for receiving a signal pattern having a plurality o! impulses oi' diierent duration, a plurality oi condensers, means for effecting a change in the charge'on each of said condensers i'or a period from a different point on said pattern to its end, the magnitude of said change depending on the length oi said period, a plurality of electroresponsive Y devices, and means for operating one 'oi' said devices depending on the combination of remaining charges on said condensers at the end oi' said pattern.

17. In a circuit for receiving a signal pattern ci' a plurality of components of different duration, a plurality oi' condensers, means for effecting a change in the charge on each oi.' said condensers for a period from a different point on said pattern to its end, the magnitude oi said change depending on the length of said period, a plurality o! electroresponsive devices and means for operating one oi said devices depending on the combination of remaining charges on said condensers, at the end of said pattern.

OLIVER T. FRANCIS.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,812,187 Ackerly June 30, 1931 2,276,689 Allen Mar. 17, 1942 1,695,840 Chauveau Dec. 18, 1928 1,956,670 Demarest May 1, 1934 2,083,849 Listrom -i June 15, 1937 2,334,575 Neiswinter Nov. 16, 1943 1,597,763 Chauveau Aug. 31, 1926 1,637,080 Kesses July 26, 1927 2,350,551 Fish June 6, 1944 FOREIGN PATENTS Number Country Date 545,399 Great Britain May 22, 1942 

